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Free keywords:
Aluminum alloys, Austenite, Binary alloys, Gallium alloys, Manganese alloys, Martensite, Product development, Temperature, Antiferromagnetic orderings, Antiferromagnetic structures, Helical modulation, Martensitic phase transitions, Martensitic transitions, Nominal composition, Propagation vector, Sample temperature, Antiferromagnetism
Abstract:
The magnetic equiatomic alloys of the nominal compositions MnNiGe0.9Al0.1 and MnNiGe0.928Ga0.072 have been investigated through the neutron powder diffraction (NPD) technique. Both these alloys undergo a martensitic phase transition from the high-temperature hexagonal (Ni2In type, with space group P63/mmc) austenite phase to the low-temperature orthorhombic (TiNiSi type, with space group Pnma) martensite phase. Our NPD analysis confirmed an incommensurate antiferromagnetic ordering of the low-temperature martensitic phase with helical modulation. The incommensurate propagation vector k is found to be (0.2065(1),0,0) and (0.2088(4),0,0) for Al and Ga doped alloys, respectively, at 1.5 K and shows a monotonic increase with increasing sample temperature. On the other hand, a commensurate antiferromagnetic ordering was observed for the high-temperature austenite phase. The incomplete martensitic transition allowed both these incommensurate and commensurate antiferromagnetic structures to coexist down to the lowest temperature of measurement (1.5 K). © 2021 American Physical Society.
